As a result, I suggested that President Obama's recent declaration on gun control was ridiculous. In response to this, my inbox was rife with comments such as: "No average citizen could build an EMP generator, but anyone can buy a gun." And: "How can destruction of our electronics kill people?"

I need to enlighten, as best I can, my reading public.

Anyone can buy an EMP gene­­­rator on Amazon for less than $300 (£200) — and I must point out that there are valid uses for EMP generators in a contained environment — that could not bring down America, but it could certainly destroy every electr­onic device in your neighbor's home (and yours as well unfortunately).

But the Amazon device that I referred to is way overpriced for its limited capabilities.

For less than $450, anyone (with a fifth-grade education) could build a device in less than half an hour that could destroy all of the electronics in a 20-story office building — permanently. There are more than 50,000 sites on the internet that provide detailed plans, free, on how to build an EMP generator that can destroy everything from a single cell phone, to a moving car, to an entire city.

To be fair, destroying all of the electronics in a city, say, the size of Cincinnati, assuming one purchased cheap Chinese components, would cost upward of $60,000. But a few people, chipping in their savings, might easily be able to raise such funds. I don't know for sure. But I do know that if someone had the funds, and the desire, and two to three days of assembly time to spare, it would be a piece of cake.

How does an EMP generator work?

Electromagnetic pulses (EMPs) are created by sudden, short bursts of an electromagnetic field. Capacitors are designed to create a sudden burst of electricity. Combined with a directional, high gain antenna, they can create an EMP.

Until recently, capacitors were generally measured in terms of microfarads (millionths of a farad) — the farad being the measure of the amount of electricity stored in the capacitor. Beginning a few years ago, however, the Chinese began creating capacitors that have reached 3,000 farads and 350 volts. Just one, combined with a high-gain directional antenna, could disable a speeding car from more than 100 feet away.

If these capacitors were purchased in volume, they could be combined in parallel or in series to create an EMP device that could fit in a small suitcase capable of taking out a high-rise office building - at a cost less than $500. A van full of them could take out the vast majority of a medium-size city, causing havoc to power stations, water-processing plants, communications, transportation, and other vital infrastructure.

Joe Raedle/Getty

EMPs are short bursts of electromagnetic radiation. Our modern electronics are highly susceptible to such short bursts of radiation — the shorter the burst, the more damage done. The first EMP testing in America happened over Hawaii in the early 1960s, with a very tiny, high-altitude nuclear explosion.

The test knocked out a few city blocks of lighting and did limited other damage. This was in the days before semiconductors had even been dreamed about. Semiconductors are millions of times more susceptible to EMP pulses than street lights. Had this test been done today, Hawaii would be in chaos.

As we move further north, the earth's electromagnetic field strengthens considerably, which amplifies any EMP event. A high-altitude nuclear explosion over Washington would be nearly 20 times as powerful as the same explosion over Hawaii.

This is something to keep in mind if you are a nation with heavy population in northern latitudes. The farther north that an EMP event occurs, the more powerful its effects will be. Most of the developed world occupies the higher northern latitudes. Something to keep in mind.

In any case, back to our subject. EMPs can be generated in many ways. Much has been said about nuclear EMPs, but that threat concerns me far less than other, more specific means of generating EMPs. The US recently announced our own EMP weapon, which can be carried aboard a missile. Using a technology based on hydraulically compressing and decompressing rods made of specific elements, the device is able to create multiple EMPs very quickly.

The weapon can be focused to take out individual buildings within a city and can take out dozens of individual buildings in a single pass of the missile. I will admit that such technology is beyond the reach of the average individual. But what if the individual is not concerned with precision strikes and merely wants to take out an entire city block or the entire city? Well, that technology is readily available, cheap, and simple to construct.

There are, of course many other ways to create an EMP. My chief technology advisor, Chris Roberts, just demonstrated a design for an EMP generator using photostrobe caps that appears to be twice as efficient as general-purpose capacitors and takes up one-10th the space. You could carry a small one in your pocket, walk down the halls of any office, and leave a trail of destroyed devices behind you.

I am not going to give a course on constructing EMP weapons. I am only trying to raise the awareness of the world to a real and imminent threat.

I also received many questions about how an EMP could kill people. The answer is easy. A large-scale localized attack that involved all of our power stations would leave us all permanently without power. An attack that included our water-processing plants would leave us without potable water, except that which we could purchase at the supermarket.

Localized attacks on food-processing plants, attacks on mass transportation, and attacks on centralized communication organizations would leave us without food and communications. Attacks on oil-processing plants would ultimately leave us without individual transportation. What percentage of the population do you think would survive such a catastrophe? And all of this without a single nuclear explosion.